Lens for semaphore signal-lights.



36566631 5G22 n I KF? a 2f/L No. 666,453. Patentd 1an. 22, wor.

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' LENs Fon sEMAPHonE SIGNAL LIGHTS." l (Applgatin ilsd )by 27, 4899.)

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UNiTnD STATES PATENT f GFFICE.

Jenn c.' n AIRD, on Boeren,l MASSACHUSETTS..

LENS Fon ssMAPi-ions s ieNAL-LIGHTS.

SPECIFICATION forming pm of Letters Peteur No. 666,453, dated January 2.2,"1901.

Application tiled May 27, 1899.

To all 'whom it may concern:

Be it known that I, JOHN C. BAIRD, of Boston, county of Suffolk, State of Massachusetts, have made certain new and usef nl lm provements in Semnphore Signal-Lights, o t which the following is a description suficiently full, clear, and exact to enable any person skilled in the art or science to which said in ventionappertnins to make and usethe same, reference being,r had to the accompanying drawings, forming a part of this specificstion, in which- Figure 'l'is a face or plan view of my improved glass panel for signahlights, and Fig. 2 a central vertical transverse section of the same.

Like letters of reference indicate correspondingparts in both figures of the drawings. My invention is designed especially to pro- 'vides colored panel for the semaphore sig nal-lightsfemployed upon railways wherein theg-fcolorshall be lxedthat is, shell give a. brilliant light at a distance of n certan color and in which the shade shall not materially change as such distance increases or decreases.

Efforts have been mede in many directions to produce a substitute for the white light in ordinary use for railway signaling to indicate safety or a clear line tothe 1ocomotiveengineers because of the numerous accidents resulting from mistaking near-by or outside lights for such signals and because of the fact that a broken panel would, particularly at great distances, produce the white eiect. As the red and green lights were' already in use Vfor danger-signals, the authorities fixed upon yellow or amber as the only distinctive color available for this purpose; but great di'icultics were experienced in utilizing this color because of the obstacles encountered in producing a stable yellow tint in the glass, the coloring-matter employed being usuztlly vegetable becnuse of the great expense attendingr the use ol metal colors for producingI a permanent yellow and such vegetnble .coloring fading rapidly. "lhis expense arose principally from the fact that :t compound of gold was deemed necessary to produce this color in glass. Moreover, even when at their best such t lenses throw so light a shade of color at great rays he delivered direct.

Serial No. 718,512. iNp modem by those convcrsant with such matters from the following explanation.

In the drawings, A represents the panel, considered as a. whole. This is preferably circular or disk-shaped, as shown; but it may of course be rectangular in form, it' desired. The thicknessof the panel is preferably about onc-querterinch,and I mix in the molten glass from which it is formed coloring matter which is compounded with a metallic base, the formulnfor which is the resultant of a long series of experi-ments in order to obtain the req- 'uisite permanency and shade of color which have been found wanting in many of the devices for this purpose. ln one face of the panel l form an annular groove f, inclosinga. circular surface g of approximately two and one-quarter inches diameter, which Isnbject to n. high polish. Outside this polished center the face of the panel is roughened or slightly corrugated at h. The rear fhce k ot' the panel is also polished smoothly over its en tire surface. ly these peculiarities of construction I attain a' double object. The slightly-roughened surface increases refraction, which so influences diffusion of the light as to prevent the shade changing materially with the distance of the observer from the signals. As the structure of the human eye is such that the color of a signal does not usually appear the seme at different distances, it is necessary for observation of the signal at great distances-say two miles--and yet maiutaining the same strong yellow color thntsome I find by a constant series of experiments that by employing the IOO highly-polished center g, inelosed by the anof yellow light; is maintuincd with no failure of the green rays, which would give un appearance of red, and such benin is distinctly visible fern distance of practically two iniles. This I also have determined ny experiment. is not the results when vthe Whole surface of the panel-is rongliened; hun, nevertheless, such irregular or wavy surface surrounding uuid polished center I have arranged it. serves to prevent radical change of color to thc observer ns he approaches t-lie light, and particularly has this proved effective in innintaiuing the color no plie eye under such adverse conditione ne fcgs, smoke, undnnnvora-blcunglcs of vision, the iight sustaining all the necessary strer ff'rh i-ud color for 'fr Signal-light. under nucl. circnuxetmiccu.

I do' not confine myself zo corrugnting cr rongliening r-lie outer portion li, of the panel face L@ any particular degree, only Snicicnlz being necessary no produce n translucent effect, nor do I confine myself to using 'the parV ticulnr size of polished cener described, as in may vary with the size of panel and oher conditione, the purpose being to produce an approximately transparenteffcct at this point.

Having t-lins explained my invention, what; I claim isl. A panel for railway signal-lights 'comprising a plate of glass colored in laire mass, one face thereof being pro vided centrally with e, smooth transparentportion and the remainder cf said face being roughened remlering:1 elle poron of the .pn-nel covered by such ronghened part, translucent.

2. The signal-light panel, A, composed of glass colored in the muss, the rear face, a, tliex'ecf being n smooth surface; the annular groove,f, in its opposite face inclosing the smooth polished surface g, and elle ronghencd eur-face, h, substantially ns Specified.

JOHN C. BAIRD.

NVM-fressen: Y

WILLIM G. REED', JOHN F. PIUTNAM'. 

